1. Field of the Invention
The present invention relates to a dynamoelectric machine such as an automotive alternator, etc., and particularly relates to a construction that improves cooling of a stator.
2. Description of the Related Art
In conventional automotive alternators, a rectangular parallelepiped lamination is prepared by laminating a predetermined number of thin strip-shaped magnetic plates such that teeth are superposed. Then, laser welding is applied to the lamination to form thin sheet coupling weld portions on outer wall surfaces of a core back at positions that divide a longitudinal direction of the lamination into four equal parts, for example, such that each extends from a first end portion to a second end portion in a direction of lamination. Next, a laminated core is prepared by bending the welded lamination into an arc shape, a fan shape, or a cylindrical shape with the teeth facing inward. Then, a cylindrical stator core is prepared by abutting end surfaces of a single laminated core or a plurality of laminated cores and welding the abutted portions thereof (see Patent Literature 1, for example).
Patent Literature 1: Japanese Patent Laid-Open No. 2002-291184 (Gazette)
A stator is mounted to a case such that a plurality of circumferential positions on two axial end surfaces of the stator core are pressed and held from two axial ends between opening edge portions of a front bracket and a rear bracket that are bowl-shaped, made of aluminum, and constitute the case. Thus, hill-shaped bulges between the thin sheet coupling weld portions of the stator core are not flattened completely, and the stator core is in a state in which circumferential portions of the end surfaces are in partial contact with the case with air interposed between the thin strip-shaped magnetic plates. Thus, one problem has been that thermal conduction from the stator core to the case deteriorates significantly, preventing effective cooling of the stator.
Moreover, it is conceivable that the number of thin sheet coupling weld portions could be increased or that thickness of the thin strip-shaped magnetic plates at the two axial ends, where the amount of deformation is greatest, could be increased as countermeasures to suppress the occurrence of gaps between adjacent thin strip-shaped magnetic plates between the thin sheet coupling weld portions. However, increasing the number of the thin sheet coupling weld portions increases costs. It is also not possible to increase the thickness of the thin magnetic plates very much if consideration is given to core loss.